Searches for n → [nbar] oscillationsand proton decay

Abstract Current status of baryon instability search is reviewed in this lecture. Proton decay with the modes and rates predicted by the original SU(5) grand unification model was not observed experimentally. The possibility of alternative baryon nonconservation scenario corresponding to the left-right symmetric unification schemes and evolving at the intermediate energy scale of ∼105 GeV is considered. One of the most spectacular manifestations of the physics of such energy scale would be an observation of neutron to antineutron transitions. Future prospects of baryon instability search are discussed.